Biomedical subjects

Gary M Skinner

Publications and source records attributed to Gary M Skinner.

3 recordsLinked to original sources

PubMed2004

Elastic properties of a single-stranded charged homopolymeric ribonucleotide.

We have investigated the elastic properties of poly(U), homopolymeric single-stranded RNA molecules that lack any base pairing and stacking interactions and conform to a random-coil structure. Using single-molecule stretching experiments we show that the elastic properties are described by a wormlike chain model for polymer elasticity rather than by a freely jointed chain model as is commonly used for single-stranded DNA. At low [Na+], introduction of a scale-dependent persistence length is required to account for electrostatic contributions.

Computer Simulation↗

PubMed2004

Single-molecule techniques for drug discovery.

Single-molecule techniques offer a number of key benefits over conventional in vitro assay methods for drug screening, as they use less material and unlock the ability to observe transient states. By observing such states, it should be possible to screen for chemical compounds that isolate these steps. The benefit of this is twofold: (a) inhibitors can be found that target key phases in biochemical processes, e.g., transcription initiation; and (b) the total number of drug targets increases as many biochemical processes consist of many transient steps, e.g., transcription promoter binding, initiation, elongation, and termination. Although single-molecule methods offer exciting opportunities for new ways of discovering drugs, there are a number of obstacles to their adoption for drug screening. The main hurdle is to develop robust apparatus that will allow many thousands of individual single molecule experiments to be performed in parallel. By using recently developed integrated microfluidics technology, this hurdle may be overcome. Here, a number of potential single-molecule approaches to drug screening are presented along with a discussion of the benefits and technical obstacles that must be overcome.

Drug Evaluation, Preclinical↗

PubMed2003

Promoter binding, initiation, and elongation by bacteriophage T7 RNA polymerase. A single-molecule view of the transcription cycle.

A single-molecule transcription assay has been developed that allows, for the first time, the direct observation of promoter binding, initiation, and elongation by a single RNA polymerase (RNAP) molecule in real-time. To promote DNA binding and transcription initiation, a DNA molecule tethered between two optically trapped beads was held near a third immobile surface bead sparsely coated with RNAP. By driving the optical trap holding the upstream bead with a triangular oscillation while measuring the position of both trapped beads, we observed the onset of promoter binding, promoter escape (productive initiation), and processive elongation by individual RNAP molecules. After DNA template release, transcription re-initiation on the same DNA template is possible; thus, multiple enzymatic turnovers by an individual RNAP molecule can be observed. Using bacteriophage T7 RNAP, a commonly used RNAP paradigm, we observed the association and dissociation (k(off)= 2.9 s(-1)) of T7 RNAP and promoter DNA, the transition to the elongation mode (k(for) = 0.36 s(-1)), and the processive synthesis (k(pol) = 43 nt s(-1)) and release of a gene-length RNA transcript ( approximately 1200 nt). The transition from initiation to elongation is much longer than the mean lifetime of the binary T7 RNAP-promoter DNA complex (k(off) > k(for)), identifying a rate-limiting step between promoter DNA binding and promoter escape.

DNA↗